package string;
import java.util.Scanner;
import java.util.Random;
public class VerificationCode {
    public static void main(String[] args) {
        String line = "0123456789abcdefghigklmnopqrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ";
        String code = "";
        Random random = new Random();

        for(int i = 0;i<4;i++){
            int index = random.nextInt(line.length());
            char c = line.charAt(index);
            code+= c;
        }
        System.out.println(code);

    }
}
